Skip to main content
NCBI home page
Annual Proceedings / Association for the Advancement of Automotive Medicine logoLink to Annual Proceedings / Association for the Advancement of Automotive Medicine
. 2003;47:147–163.

Incidence of Elderly Eye Injuries in Automobile Crashes: The Effects of Lens Stiffness as a Function of Age

Gail A Hansen 1, Joel D Stitzel 1, Stefan M Duma 1
PMCID: PMC3217536  PMID: 12941223

Abstract

The purpose of this paper is to elucidate the incidence of eye injuries with respect to occupant age in frontal automobile crashes as well as to investigate possible injury mechanisms of the elderly eye and the effects of lens stiffness. The National Automotive Sampling System was searched from years 1993–2000 for three separate occupant age groups of 16–35 years old, 36–65 years old, and 66 years old and greater in order to compare the total number of weighted occupants who sustained an eye injury to the number of occupants who sustained an eye injury per age group. Three separate impact scenarios simulating a foam particle (30 m/s), a steering wheel (15 m/s), and an air bag (67 m/s), were applied to a finite element eye model in order to elucidate the effects of aging on the eye when subjected to blunt trauma. The lens stiffness of the model was varied according to human lens stiffness values determined for each age group. Occupants aged 66 years old and greater were two to three times more likely to incur an eye injury than younger occupants. The computational eye model demonstrated that increased risk was related to the increasing stiffness of the lens, producing up to a 120% larger stress in the ciliary body.

Due to considerable advancements in medicine over the last several decades, the mortality rate is on the decline. As of 2001, there were more than 25 million people aged 70 years or greater in the United States, and in 2000 this age group made up 9.1% of the total U.S. population. Elderly people aged 70 years and older accounted for 10 percent of all licensed drivers in 2000 as compared to only 8 percent in 1990, indicating that the number of elderly drivers is on the rise as well (NHTSA, 2001). While there are many topics within the realm of elderly research, this study addresses the mechanical strength of the aging lens and its effect on the occurrence of eye injuries in the elderly population. Numerous discoveries have revealed a relationship between age and certain mechanical characteristics of the eye, in particular, those relating to the lens, lens capsule, and cornea (Fisher, 1969, 1971; Krag, Olsen, Andreassen, 1997; Yamada, Evans, 1970).

Eye injuries are expensive to treat, affect a large portion of the population, and often result in long-term disability (Schein et al., 1988). Medical literature is replete with case studies on air bag-induced eye injuries (Duma et al., 1996; Ghafouri et al., 1997; Vichnin et al., 1995: Stein, Jaeger, Jeffers, 1999). For each of these papers, there was a wide range of ocular injuries reported, from a minor eyelid or corneal abrasion, to a more severe globe rupture or lens dislocation. Duma et al. (2002) determined the overall risk and severity of eye injuries in automobile crashes and explained the effect of frontal air bags on these patterns. A new four-level eye injury severity scale was developed that quantifies injuries based on recovery time, need for surgery, and possible loss of sight. Using these levels, it was shown that while occupants in frontal crashes exposed to an air bag deployment (3.1%) sustained an eye injury more often than occupants not exposed to an air bag deployment (2.0%), the air bag provided a beneficial exchange by decreasing the incidence of more severe orbital fractures. Moreover, this study found that orbital fractures accounted for 0% of all eye injuries obtained in automobile crashes with an air bag exposure and less than 1% of all eye injuries sustained in crashes not involving an air bag exposure. Furthermore, the soft tissue regions incurred 99% of all eye injuries, with 15–25% of these being severe injuries such as hyphemas and globe ruptures. While the majority of eye injuries were minor, the 15–25% severe injuries were located in the lens, ciliary body, and scleral regions; regions that have been shown to change with age.

There is a limited amount of experimental data regarding air bag-induced eye injuries in comparison to the number of individual case study publications. Experimentation performed by Fukagawa, Tsubota, and Kimura (1993), and Duma and Crandall (2000), illustrated the compounding risk of eye injuries not only from air bag contact, but also from particles released from the module during deployment. Of the many existing case studies and limited experimental research involving air bag-induced eye injuries, none have been performed with regard to the effect of occupant age.

Although computational modeling of the human eye has been studied, the majority of models created were designed for static solutions and not for impact trauma studies (Bryant, McDonnell, 1996; Hanna et al., 1989; Sawusch, McDonnell, 1992; Wray, Best, Cheng, 1994). More recently, a finite element model of the human eye was presented by Kisielewicz (1998) and Uchio (1999) for use in dynamic events. While this model provided useful insights as the first dynamic model, its non-biofidelic boundary conditions and lack of thorough validation experimentation made it difficult to use for injury prediction at high rates. Stitzel et al. (2002) performed a series of eye experiments with foam particles, BBs, and baseballs for validation and development of the Virginia Tech Eye Model (VTEM), a finite element eye model used to predict globe rupture due to high-speed blunt impact.

The purpose of this study was to elucidate the incidence and severity of eye injuries with respect to occupant age in frontal automobile crashes. The goals of this research were to investigate injury mechanisms of the elderly eye and the effects of lens stiffness through the use of a finite element eye model to reveal the effects of aging on the eye when subjected to blunt trauma.

EYE ANATOMY

The exterior of the eye, referred to as the corneoscleral shell, consists of the transparent cornea on the anterior surface and the white sclera comprising the rest of the globe surface (Figure 1). The anterior surface of the cornea is covered with epithelial cells while the posterior, or interior, surface is covered by a layer of endothelial cells. The ciliary body supports the lens through the zonules and provides the mechanism for accommodation. The anterior chamber contains the volume of fluid between the cornea and the lens, known as the aqueous humor, while the vitreous body is the volume of fluid posterior to the lens. The retina is the light-transducing inner layer of the sclera (Westmoreland, Lemp, 1997).

Figure 1.

Figure 1

Open in a new tab

Primary ocular structures.

METHODS

A two-part study is presented to investigate the risk of eye injuries in the elderly driving population. The purpose of the first part is to elucidate the incidence and severity of eye injuries with respect to occupant age in frontal automobile crashes. The purpose of the second part is to investigate injury mechanisms of the elderly eye and the effects of lens stiffness through the use of a finite element eye model to reveal the effects of aging on the eye when subjected to blunt trauma.

PART I: CASE STUDY ANALYSIS

In order to remove the inaccuracy associated with small case study projections, the National Automotive Sampling System (NASS) database was employed for this study. The NASS database has been utilized for national injury projection studies to analyze injury severity and crash characteristics in search of useful information such as safety system interaction, injury severity, and type of impact (Atkinson T, Atkinson P, 2000; Duma et al., 1996; Duma et al., 2002; Farmer, Braver, Mitter, 1997). Every crash investigated for the NASS database is assigned a weighted value, which scales the incidence of a particular crash to a number representing the actual occurrence of similar uninvestigated crashes occurring each year in the U.S. Unweighted numbers reflect actual values based upon the number of cases that appear in the NASS database. Weighted occupants and unweighted cases were analyzed.

Injuries were coded by trained nurses and crash investigators using the Abbreviated Injury Scale (AIS) (AAAM, 1998). In addition to the AIS identification system, this study incorporated the use of a new eye injury grouping method that was developed to assess the severity of eye injuries based on both the need for ocular surgery and the potential for loss of sight (Duma et al., 2002). The basic AIS system does not address either of these criteria, as it only considers the overall threat to life. Almost all eye injuries are coded as minor, AIS1, in the basic system. This new grouping method splits AIS coded eye injuries into more divisions, or levels, to compare the severity of eye injuries in automobile crashes from the NASS database. Of these new divisions, Level 1 includes minor injuries to the skin surrounding the eye such as an eyelid abrasion or laceration; Level 2 injuries are minor injuries to the eye such as corneal abrasions or injuries to the vitreous; Level 3 includes more serious eye injuries that may require surgery and present a guarded long-term prognosis such as corneal lacerations and orbital fractures; Level 4 injuries are the most serious eye injuries that would result in blindness, such as an eye avulsion or enucleation.

For this study, NASS cases were selected from the years 1993 through 2000 that included passenger cars and light trucks, drivers and front seat occupants only, excluding ejected occupants and rollovers. In addition, only frontal impacts were considered, which were defined as having a primary direction of force (PDOF) of 11, 12, or 1 o’clock. Eye injuries were defined as damage to the periorbital skin, globe, or orbital bones.

This study was divided into two analyses: Analysis I identifies the relationship between age and risk for eye injury in a crash; Analysis II identifies a relationship between age and risk for serious eye injury (new eye injury severity scale - Level 2 and greater) in a crash. Statistical analysis was performed using the chi square test of independence for survey data (SUDAAN, Research Triangle Park, North Carolina). Percentages and p-values were calculated for each of the variables.

Analysis I

For each specific year the total cases and total weighted occupants were sorted into age categories of 16–35 years old, 36–65 years old, and 66 years old and greater, and then divided into three sets. The first set comprised crashes with and without an air bag exposure. Due to a combination of air bag and non-air bag deployment cases, sources of injury included items such as the windshield, steering wheel, and air bag. The second set only included crashes involving an air bag exposure. Eye injuries suffered in these crashes were primarily attributed to an air bag deployment. The third set included only crashes not involving an air bag exposure, meaning that all eye injuries sustained were attributed to sources other than an air bag. For each of these three sets, the total number of weighted occupants sustaining an eye injury was compared to the total number of weighted occupants who did not sustain an eye injury.

Analysis II

The three sets of data, as described in Analysis I, were divided into four levels based upon the new AIS eye injury severity levels (Duma et al., 2002). For this analysis all Level 1 severity injuries, including minor injuries to the skin surrounding the eye, such as an eyelid abrasion or laceration, were removed, leaving only eye injury severities of Levels 2 through 4, such as corneal abrasions and injuries to the vitreous, corneal lacerations and orbital fractures, and eye avulsions and enucleations. This allowed for an analysis neglecting minor eye injuries, in order to determine a relationship between age and risk for severe injuries, such as globe rupture or lens dislocation.

PART II: COMPUTATIONAL EYE MODEL

The VTEM was utilized to investigate injury mechanisms of the elderly eye in comparison to younger age groups, and the effects of lens stiffness when subjected to blunt trauma (Stitzel et al., 2002) (Figure 2). Specifically, with the use of this eye model, a parametric study was performed to determine stress distributions across each age group of 16–35 years old, 36–65 years old, and 66 years old and greater, when subjected to three generalized impact configurations. The detailed eye model included the corneoscleral shell, which consisted of the cornea, sclera, and limbus, and was characterized by the region where the cornea and sclera join in the anterior portion of the eye. These ocular structures were represented by a mesh with Lagrangian formulations for element properties, and were located inside a mesh that used a Eulerian representation for fluid flow. This model had a total of 10,020 solid and shell elements. Dynamic modeling was performed using LS-Dyna.

Figure 2.

Figure 2

Open in a new tab

VTEM - Lagrangian mesh of eye showing corneoscleral shell, lens, zonules, and ciliary body (Stitzel, 2002).

Simulation Test Matrix

In order to investigate a range of possible eye injury mechanisms in automobile crashes, a test matrix comprised of 9 simulations, three separate impact scenarios for each of three age groups (lens stiffnesses), was developed. The resulting peak stress and location in the corneoscleral shell, ciliary body, and zonules were analyzed (Table 1). By identifying the peak stress at multiple sites within the eye, injury severity could be assessed for each impact scenario, assuming lens dislocation due to high stresses in the ciliary body or zonules, or globe rupture caused by a tear in the corneoscleral shell. These impacts simulated a foam particle (30 m/s), a steering wheel (15 m/s), and an air bag (67 m/s). The steering wheel and air bag impact scenarios were indicative of those experienced in automobile crashes severe enough to cause globe rupture or other serious eye injuries.

Table 1.

Simulation Test Matrix Per Age Group.

Object Length of Simulation (ms) Mass (g) Velocity (m/s) Kinetic Energy (Joules) Number of Elements Elastic Modulus (MPa)
Foam 0.4 0.077 30.0 0.035 256 2.21
Steering Wheel 0.6 28.8 15.0 3.24 900 2.82
Air Bag 0.3 28.2 67.0 63.4 400 300
Open in a new tab

The foam was modeled using 8-node bricks and a linear elastic material (Figure 3a). The air bag was created using 4-node shell elements, and was modeled using the air bag fabric model within ls-dyna (Figure 3b). This material model is a variation of the orthotropic material model that does not develop stresses to resist compression or bending. A linear elastic liner was added to the air bag fabric, which was 5% of the thickness of the air bag fabric, giving the fabric additional stability. The steering wheel was modeled using the cross sectional geometry of a common steering wheel (Figure 3c). The steering wheel consisted of a u-shaped aluminum core surrounded by foam. The core was modeled with the density of aluminum and was approximated as stiff because of its high elastic modulus in comparison to the eye. A cylindrical specimen of the steering wheel foam was tested in uniaxial compression to obtain an elastic modulus. The foam in the steering wheel was modeled using a linear elastic approximation. All components of the steering wheel were modeled using 8-node brick elements.

Figure 3.

Figure 3

Open in a new tab

Foam particle (a), air bag fabric (b), and steering wheel (c) impact simulations to the eye.

Lens stiffness values were varied according to age group by data obtained from relevant literature. The lens was modeled as linearly elastic, isotropic, and incompressible using force-displacement data from Czygan and Hartung (1995) who performed tests on human lens nuclei. Due to the lack of true lens stiffness values available within previous research, the average modulus of elasticity for a person of age 66 years old and greater was calculated to be 6.888 MPa using the force-displacement plots. Then this elastic modulus was correlated to an average value of equatorial elastic modulus of the same age group on Fisher’s plot of Young’s modulus of equatorial elasticity versus age (Fisher, 1971). Based upon the assumption that Young’s modulus of elasticity and Young’s modulus of equatorial elasticity follow the same trend with respect to age, the plot of equatorial elasticity was used to extrapolate values of elastic modulus for the other two age groups (Table 2). The lens stiffness values, determined by the relationship between the two types of moduli, corresponded well to the stiffness values of other ocular components modeled in the VTEM, such as the cornea (1.24 MPa), sclera (3.58 MPa), and ciliary body (11 MPa). The stiffness of the human lens increased by 100% between age groups of 16–35 years old and 36–65 years old (Table 2). A 233% increase was observed between age groups of 16–35 years old and 66 years old and greater. Therefore, the average stiffness of a 16–35 year old lens was 30% that of an elderly (66 years old and greater) lens.

Table 2.

Lens Elastic Modulus Values By Age Group.

Age Group(Years) Fisher Equatorial Elastic Modulus Czygan & Hartung Elastic Modulus (MPa) Scaled Elastic Modulus (MPa)
(KPa) (%)
16–35 1.1 30% N/A 2.064
36–65 2.2 60% N/A 4.128
66-greater 3.6 100% 6.888 6.888
Open in a new tab

To examine the variation in response of the lens-zonules-ciliary complex per age group, differences in stress response during the initial period of loading, which usually corresponded to the first peak stress, were compared. Peak stress in the corneoscleral shell was reported for the location experiencing the maximum stress overall. This locality corresponded to the limbus for the foam particle impacts, and the anterior portion of the equator for the air bag and steering wheel impacts. For comparison of stress in the zonules, the peaks were recorded at the posterior interface between the zonules and the lens. Similarly, the peak stresses in the ciliary body were taken from the posterior insertion point of the zonules to the ciliary body.

RESULTS

A total of 11,494,824 weighted occupants from 25,131 cases was included in this study for the 8-year period from 1993 through 2000. This study examined eye injuries obtained by occupants of age groups 16–35 years old, 36–65 years old, and 66 years old and greater, exposed, not exposed, and a combination of both, to an air bag deployment in a vehicle crash. As occupant age increased, the number and severity of eye injuries sustained by occupants involved in a crash with or without an air bag deployment, also increased. The computational eye model demonstrated that increased lens stiffness produced larger stresses in the ciliary body and changes in the response of the lens-zonules-ciliary body complex.

PART I: CASE STUDY ANALYSIS

Analysis I

The overall risk of eye injury for occupants aged 66 years old and greater, both exposed and not exposed to an air bag deployment, was higher at 4.46%, but not significantly, than age groups of 16–35 years old and 36–65 years old at 2.27% and 2.40%, respectively (p = 0.21, p=0.24). Furthermore, when only examining eye injuries sustained by occupants exposed to an air bag deployment in a crash, occupants aged 66 years old and greater maintained a higher risk of 6.29%, but not significantly, while age groups of 16–35 years old and 36–65 years old obtained a risk of 3.64% and 2.24%, respectively (p=0.59, p=0.33) (Figure 4). Moreover, when analyzing vehicle crashes without air bag exposure, it was found that again the risk of eye injury to ages 66 years old and greater was found to be higher at 4.11% than for ages 16–35 years old and 36–65 years old at 1.96% and 2.52%, respectively (p=0.11, p=0.24) (Figure 5).

Figure 4.

Figure 4

Open in a new tab

Incidence of all eye injuries for occupants exposed to an air bag deployment (1993–2000).

Figure 5.

Figure 5

Open in a new tab

Incidence of all eye injuries for occupants not exposed to an air bag deployment (1993–2000).

Analysis II

The overall risk for serious eye injury (Level 2 severity and greater) was found to be 0.77% for occupants aged 66 years old and greater, whereas age groups of 16–35 years old and 36–65 years old maintained a risk of 0.31% and 0.53%, respectively (p=0.08, p=0.36) (Figure 6). For air bag deployments alone, occupants aged 66 years old and greater sustained an increased risk of 1.24% in comparison to age groups of 16–35 years old and 36–65 years old of only a 0.73% and 0.58% risk, respectively (p=0.20, p=0.04). Finally, in cases without air bag deployments, occupants aged 66 years old and greater had a higher risk of 0.65%, while age groups of 16–35 years old and 36–65 years old had a risk of 0.20% and 0.52%, respectively (p=0.05, p=0.62).

Figure 6.

Figure 6

Open in a new tab

Occupants with eye injuries of Level 2 severity and greater both exposed and not exposed to an air bag deployment.

PART II: COMPUTATIONAL EYE MODEL

A matrix comprised of 9 impact simulations, 3 for each age group, was developed to analyze the resulting stresses and their locations in the corneoscleral shell, ciliary body, and zonules (Table 3). The differences in stress response between each age group were analyzed during the initial loading, which typically corresponded to the first peak stress.

Table 3.

Stress Data for Impact Simulations.

Simulation # Object Age Group (Yrs) Stress (MPa)
Shell Ciliary Body Zonules
F1 Foam (16–35) 7.82 2.83 16.40
F2 Foam (36–65) 7.77 2.75 14.75
F3 Foam (66-greater) 7.82 2.58 12.83
W1 Wheel (16–35) 12.76 4.25 37.86
W2 Wheel (36–65) 12.83 6.28 35.25
W3 Wheel (66-greater) 12.77 9.35 31.62
A1 Air Bag (16–35) 15.30 8.81 33.04
A2 Air Bag (36–65) 15.13 8.88 28.34
A3 Air Bag (66-greater) 15.10 9.36 24.01
Open in a new tab

When analyzing the ciliary body during the three impacts, it was found that the stress generally increased with increasing age or lens stiffness (Figure 7). The peak stress in the ciliary body was up to 2.2 times greater for the elderly lens stiffness value when compared to that of younger lens stiffness values. There was an increase in the peak stress for the air bag impacts with increasing lens stiffness, but this change was not very sensitive to lens stiffness changes. When looking at the zonular stresses, they were in general much more sensitive to changes with changing lens stiffness. The stress in the zonules decreased with increased age or lens stiffness for the three impact simulations. Furthermore, peak deformation of the lens decreased due to an increased lens stiffness corresponding to aging, when impacted (Figure 8). It was found that the air bag simulation caused the highest stresses in the ciliary body and corneoscleral shell, whereas the steering wheel produced the highest stresses in the zonules, of all of impact scenarios.

Figure 7.

Figure 7

Open in a new tab

Stress changes in ciliary body due to increased lens stiffness for three impact scenarios.

Figure 8.

Figure 8

Open in a new tab

Changes in peak deformation of the lens due to varying lens stiffness when impacted by foam particle (30 m/s).

DISCUSSION

The relationship between age and the mechanics of various ocular components, particularly stiffening of the lens, is supported by previous research. General testing of the mechanical characteristics of the entire lens suggest that aging of the human lens is associated with a progressive loss of mechanical strength (Fisher, 1969, 1971; Krag et al., 1997; Yamada et al., 1970). As research data implies, the gradual change in lens stiffness over a lifetime can lead to a stiff lens; one that is approximately 4 times stiffer than at birth (Fisher, 1971). As stiffness of the interior lens components increase over time, the amount of deformation that the lens can withstand without damage or dislocation decreases (Fisher, 1971). This can result in an increased risk of eye injury with age. Moreover, a number of studies acknowledge the fact that the mechanical integrity of the eye is reduced after vision correction procedures, such as photorefractive keratectomy (PRK), automated lamellar keratoplasty (ALK), and laser assisted in situ keratomileusis (LASIK), that involve corneal incisions, and that negative effects persist years after the procedure (Glasgow et al., 1988; Lindquist, 1992; McDonnell et al., 1987; Pearlstein et al., 1988; Zhaboyedov, Bondavera, 1990). The elderly are more likely to have these procedures performed and are therefore more likely to sustain eye injuries because of them.

Many of the recent comprehensive studies investigating eye trauma do not specifically address the question of age (Viestenz, Kuchle, 2001; Moshetova et al., 2002). However, Moshetova et al. (2002), in a study of 426 patients with blunt injuries to the eye, demonstrated that the most frequent complication of blunt injury to the eye was hemorrhage to the anterior chamber, or hyphema in 57.57% of cases. It is well known that tears of the ciliary body or iris, which are the more vascularized muscles of the interior of the eye, often result in hyphemas. However, without looking at the same datasets for trends based on age, it is impossible to tell if the increased stress in the ciliary body with increasing lens stiffness is an indicator of increased susceptibility of the eye to hyphema with age. It does, however, provide an indication of what the eye trauma research community should focus on in the future. It is clear from the finite element model that by changing lens stiffness one alters the response of the eye, increasing stresses in the ciliary body and decreasing stresses in the zonules. Whether this explains a shifting in eye injury patterns (i.e. a shift from zonular tears for the younger population versus ciliary body injury and hyphema for the older population) is a question that needs to be answered by looking at the NASS data for trends with respect to age. In that sense, the current work indicates that finite element modeling can aid in the understanding of mechanisms that may manifest themselves in the injury distribution seen in the field.

It is possible that the zonular stresses are more sensitive to the deformation of the lens, while the ciliary body stresses are more sensitive to the stiffness of the lens-zonule complex. Since the stiffness of the ciliary body (11 MPa) used for the older population (66+, 6.88 MPa) in the current study is close to the stiffness of the lens, the response of the ciliary body could be expected to more closely follow that response. The stiffness of the zonules, 358 MPa, may make the peak stresses developed in them less sensitive to stiffness changes in the lens, and more sensitive to changes in the deformation of the lens-zonule-ciliary body complex. There is less deformation of this lens-iris-ciliary body ‘diaphragm’ for the higher stiffnesses, and there is a decrease in peak stress in the zonules along with this decreasing deformation. However, there is generally an increase in the peak stress in the ciliary body with increasing lens stiffness. It is not unlikely that geometry and deformation play a large factor in the peak stress analyses. The peak stresses in the ciliary body occurred nearly always in the posterior portion of the ciliary body where the zonules insert. The peak stresses in the zonules occurred nearly always in the posterior portion of the zonules where the lens inserts. This demonstrates that the tensile forces acting upon the posterior portion of the ‘diaphragm’ of the eye are likely the important forces to be considered as potential eye injury mechanisms. Since these stresses are not uniform throughout the ciliary body and zonules, it is clear that geometry plays a strong role in the response of the eye.

In terms of globe stresses, the lack of a trend toward increased globe stress with increasing lens stiffness points toward other mechanisms dominating the response of the eye to trauma. It is well known that the sclera tends to thin with age, and this is a potential factor as well. However, scleral thinning was not modeled. By modeling the increased lens stiffness and not obtaining an increased stress in the corneoscleral shell, one can eliminate the increase of lens stiffness itself as a potential implicating factor to explain the increased incidence of globe rupture found in this study. This implies that there are other changes, such as scleral thinning and perhaps an increased overall susceptibility of the tissues themselves, to rupture. It should be an objective of future work to correlate these changes to increased risk of globe rupture with increasing age.

CONCLUSION

Of the total 11,494,824 weighted occupants from 25,131 cases included in this study for the 8-year period from 1993 through 2000, weighted occupants aged 66 years old and greater were two to three times more likely to sustain an eye injury compared to younger age groups when exposed and not exposed to an air bag deployment in a vehicle crash. Also, when examining the most serious eye injuries, the overall risk for globe rupture was 1.7 (air bag exposure) to 3.3 (non air bag exposure) times greater for elderly occupants aged 66 years old and greater as compared to younger occupants age groups. The overall risk for serious eye injury (new eye injury severity scale - Level 2 severity and greater) in a crash was found to be significantly higher for occupants aged 66 years old and greater when compared to occupants aged 16–35 years old, in non-air bag deployment or combination cases (p=0.08, p=0.05). In the case of collisions with air bag deployments only, occupants aged 66 years old and greater sustained a significantly increased risk in comparison to those aged 36–65 years old (p=0.04). These relationships can be explained partly by aging of the human lens (Fisher, 1969, 1971; Krag et al., 1997; Yamada et al., 1970).

The computational eye model demonstrated that there was an increase in peak stress in the posterior portion of the ciliary body along with a decrease in peak stress in the posterior portion of the zonules, with increasing lens stiffness. The peak stress in the ciliary body was up to 2.2 times greater for the elderly lens stiffness value when compared to that of younger lens stiffness values. Furthermore, peak deformation of the lens decreased due to an increased lens stiffness, corresponding to aging, when impacted. Based upon the NASS and computational modeling analyses, the risk for eye injury increases with age and as a result, the elderly are more likely to obtain eye injuries in traumatic impact situations.

REFERENCES

  1. Association for the Advancement of Automotive Medicine (AAAM) The Abbreviated Injury Scale (AIS) 1998 Revision. Des Plains, IL: 1998. [Google Scholar]
  2. Atkinson T, Atkinson P. Knee injuries in motor vehicle collisions: a study of the National Accident Sampling System database for the years 1979–1995. Accident Analysis and Prevention. 2000 Nov;32(6):779–86. doi: 10.1016/s0001-4575(99)00131-1. [DOI] [PubMed] [Google Scholar]
  3. Bryant M, McDonnell P. Constitutive laws for biomechanical modeling of refractive surgery. Journal of Biomechanical Engineering. 1996 Nov;118:473–481. doi: 10.1115/1.2796033. [DOI] [PubMed] [Google Scholar]
  4. Czygan G, Hartung C. Mechanical testing of isolated senile human eye lens nuclei. Medicine Engineering and Physics. 1996 Jul;18(5):345–349. doi: 10.1016/1350-4533(95)00076-3. [DOI] [PubMed] [Google Scholar]
  5. Duma S, Crandall J. Eye injuries from airbags with seamless module covers. Journal of Trauma. 2000 Apr;48(4):786–9. doi: 10.1097/00005373-200004000-00036. [DOI] [PubMed] [Google Scholar]
  6. Duma S, Jernigan M, Sitizel J, Herring I, Crowley J, Brozoski F, Bass C. The effect of frontal air bags on eye injury patterns in automobile crashes. Archives of Ophthalmology. 2002 Nov;120(11):1517–22. doi: 10.1001/archopht.120.11.1517. [DOI] [PubMed] [Google Scholar]
  7. Duma S, Kress T, Porta D, Woods C, Snider J, Fuller P, Simmons R. Air bag induced eye injuries: A report of 25 cases. Journal of Trauma. 1996;41(1):114–119. doi: 10.1097/00005373-199607000-00018. [DOI] [PubMed] [Google Scholar]
  8. Farmer C, Braver E, Mitter E. Two-vehicle side impact crashes: The relationship of vehicle and crash characteristics to injury severity. Accident Analysis and Prevention. 1997 May;29(3):399–406. doi: 10.1016/s0001-4575(97)00006-7. [DOI] [PubMed] [Google Scholar]
  9. Fisher R. Elastic constants of the human lens capsule. Journal of Physiology. 1969;201:1–19. doi: 10.1113/jphysiol.1969.sp008739. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Fisher R. The elastic constants of the human lens. The Journal of Physiology. 1971;212:147–180. doi: 10.1113/jphysiol.1971.sp009315. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Fukagawa K, Tsubota K, Kimura C, et al. Corneal endothelial cell loss induced by air bags. Opthalmalogy. 1993 Dec;100(1819):23. doi: 10.1016/s0161-6420(13)31394-3. [DOI] [PubMed] [Google Scholar]
  12. Ghafouri A, Burgess S, Hrdlicka Z, Zagelbaum B. Air bag related ocular trauma. American Journal of Emergency Medicine. 1997 Jul;15(4):389–92. doi: 10.1016/s0735-6757(97)90135-2. [DOI] [PubMed] [Google Scholar]
  13. Glasgow B, Brown H, Aizuss D, Mondino B, Foos R. Traumatic dehiscence of incisions seven years after radial keratotomy. American Journal of Ophthalmology. 1988;106:703–7. doi: 10.1016/0002-9394(88)90704-0. [DOI] [PubMed] [Google Scholar]
  14. Hanna K, Jouve F, Waring G, Ciarlet P. Computer simulation of arcuate and radial incisions involving the corneoscleral limbus. Eye. 1989;3:227–239. doi: 10.1038/eye.1989.32. [DOI] [PubMed] [Google Scholar]
  15. Krag S, Olsen T, Andreassen T. Biomechanical characteristics of the human anterior lens capsule in relation to age. Investigative Ophthalmology & Visual Science. 1997 Feb;38(2):357–63. [PubMed] [Google Scholar]
  16. Lindquist T. Complications of corneal refractive surgery. International Ophthalmology Clinics. 1992;32:97–114. doi: 10.1097/00004397-199223000-00008. [DOI] [PubMed] [Google Scholar]
  17. Lueder G. Airbag associated ocular trauma in children. Journal of Ophthalmology. 2000;107(8):1472–1475. doi: 10.1016/s0161-6420(00)00176-7. [DOI] [PubMed] [Google Scholar]
  18. McDonnell P, Lean J, Schanzlin D. Globe rupture from blunt trauma after hexagonal keratotomy. American Journal of Ophthalmology. 1987;103:241–2. doi: 10.1016/s0002-9394(14)74243-6. [DOI] [PubMed] [Google Scholar]
  19. Moshetova L, Bendelik E, Alekseev I, Zhitenev V, Aleksandrova T, Tabekova T. Contusions of the eye, their clinical picture and outcomes. Vestnik oftalmologii. 1999;115(3):10–3. [PubMed] [Google Scholar]
  20. National Highway Traffic Safety Administration (NHTSA), National Automotive Sampling System (NASS) Crashworthiness Data System, 1993–2000. Department of Transportation (DOT) HS 808985, 8; Washington D.C.: 2000. [Google Scholar]
  21. National Highway Traffic Safety Administration (NHTSA), National Center for Statistics & Analysis (NCSA) Department of Transportation (DOT) HS 809475, Traffic Safety Facts 2001, Older Population; Washington D.C.: 2001. [Google Scholar]
  22. Pearlstein E, Agapitos P, Cantrill H, Holland E, Williams P, Lindstrom R. Ruptured globe after radial keratotomy. American Journal of Ophthalmology. 1988;106:755–6. doi: 10.1016/0002-9394(88)90724-6. [DOI] [PubMed] [Google Scholar]
  23. Sawusch M, McDonnell P. Computer modeling of wound gape following radial keratotomy. Refractive and Corneal Surgery. 1992;8:143–145. [PubMed] [Google Scholar]
  24. Schein O, Hibberd P, Shingleton B, Kunzweiler T, Frambach D, Seddon J, Fontan N, Vinger P. The spectrum and burden of ocular injury. Journal of Ophthalmology. 1988;95(3):300–305. doi: 10.1016/s0161-6420(88)33183-0. [DOI] [PubMed] [Google Scholar]
  25. Stein J, Jaeger E, Jeffers J. Air bags and ocular injuries. Transactions of the American Ophthalmological Society. 1999;97:59–82. [PMC free article] [PubMed] [Google Scholar]
  26. Stitzel J, Duma S, Cormier J, Herring I. A nonlinear finite element of the eye with experimental validation for the prediction of globe rupture. Stapp Car Crash Journal. 2002 Nov;46:81–102. doi: 10.4271/2002-22-0005. [DOI] [PubMed] [Google Scholar]
  27. Vichnin M, Jaeger E, Gault J, Jeffers J. Ocular injuries related to air bag inflation. Journal of Ophthalmic Plastic and Reconstructive Surgery. 1995 Nov-Dec;26(6):542–8. [PubMed] [Google Scholar]
  28. Viestenz A, Kuchle M. Retrospective analysis of 417 cases of contusion and rupture of the globe with frequent avoidable causes of trauma: the Erlangen Ocular Contusion-Registry (EOCR) 1985–1995. Klinische Monatsblatter fur Augenheilkunde. 2001;218(10):662–9. doi: 10.1055/s-2001-18388. [DOI] [PubMed] [Google Scholar]
  29. Westmoreland B, Lemp M. Clinical Anatomy of the Eye. 2. Blackwell Sciences Inc.; 1997. ISBN 063204344X. [Google Scholar]
  30. Wray W, Best E, Cheng L. A mechanical model for radial keratotomy: toward a predictive capability. Journal of Biomechanical Engineering. 1994;116:56–61. doi: 10.1115/1.2895705. [DOI] [PubMed] [Google Scholar]
  31. Yamada H, Evans F. Strength of Biological Materials. Baltimore: Williams & Wilkins; 1970. [Google Scholar]
  32. Zhaboyedov G, Bondavera G. Traumatic rupture of the eyeball after radial keratotomy. Vestnik Oftalmologii. 1990;106:64–5. [PubMed] [Google Scholar]

Articles from Annual Proceedings / Association for the Advancement of Automotive Medicine are provided here courtesy of Association for the Advancement of Automotive Medicine

RESOURCES